The invention relates to a fastening pin (11) for fittings of windows, doors or similar, comprising a bottom part (13) for arranging the fastening pin (11) on a moveable operating rod of a respective fitting, and comprising a top part (15) for locking engagement into a closure part associated with the fitting depending on a respective position of the operating rod, wherein the top part (15) comprises an inner pin (17) that extends along a top part axis (K) away from the bottom part (13), as well as a sleeve (19) that is mounted such that it can move axially in the direction of the top part axis (K), in order to permit an adapting of the axial length of the top part (15) for a precisely fitting engagement in the closure part. In addition, retaining means (35, 37, 39, 41) for retaining the sleeve (19) in a defined axial position are provided on the top part (15).